Improvement of fish passage in culverts using CFD

Upstream migration of fish through circular culverts is often prevented by velocities in the barrel being higher than that of the natural channel. In this investigation a computational fluid dynamic (CFD) model has been used to test the effects of various spoiler baffle geometries in culverts of varying size to reduce water velocity and increase water depth and thus increase the upstream passage of small fish species. Results indicated that standard baffles designed for specific fish species or groups could be successfully retrofitted to culverts of varying dimensions. Subsequent field tests have confirmed the effectiveness of the design.

► Spoiler baffles in culverts are the optimum solution for fish migration.
► Not only reducing the flow velocity but also providing resting areas is essential.
► CFD is a reliable tool for the design of new and restoration of existing culverts.
► Spoiler size depends more on the type of migrating species than on culvert size.